The objective of this research project is to indicate a role for nonmuscle actin and myosin in the morphological changes sperm undergo during maturation in the male reproductive tract and capacitation in the female reproductive tract prior to fertilization. The goals for the current year are 1) to identify and localize actin in the mammalian testis and 2) to pursue the biochemical characterization of sperm actin and myosin. The elucidation of the distribution of actin in Sertoli cells and spermatids will contribute to our understanding of the complex process of differentiation which results in fertile sperm cells. The biochemical characterization of sperm actin and myosin may indicate unique properties of these proteins which will contribute to our understanding of their function in physiological processes relevant to fertility. The regulation of sperm myosin may be of importance to spermiogenesis and/or capacitation, the acrosome reaction and fertilization. Work in progress includes 1) pursuit of sufficient amounts of pure sperm actin to compare with other bovine actin isozymes; 2) investigating physiological or metabolic states of sperm cells which may result in activation of a quiescent sperm myosin; possible mechanisms for regulation of sperm myosin may involve cAMP, calcium or protein phosphorylation; 3) immunofluorescent localization of actin in suspensions of unseparated cells dispersed from seminiferous tubules; and 4) identification of actin in hamster spermatozoa undergoing an acrosome reaction.